The present invention relates to working components in force sensors and more particularly to force sensor components having an operable irregular surface topography which comprises a plurality of interconnecting ridges which reinforce each other against bending.
There has developed a need for pressure sensitive conductive components. For an electrical switch which normally has only on and off positions, a need has arisen in the ability of the switch to vary current flow with the degree of pressure between the components which close the switch. Such force sensor components could be incorporated into music synthesizers such as keyboards, drums, woodwinds, and the like where the touch of the musician may determine the volume, timbre, or the like of the instrument. Similarly such force sensitive components could be incorporated into product components for computers (e.g., graphics pads), television, and stereo controllers, security pressure sensors, biomedical devices, robots and household appliances.
The force sensor components of the invention may be used for purposes of making direct contact with or being used in close proximity with conductive circuitry. The performance of the force sensor components herein at different pressures could be utilized to vary a variety of different electrical properties such as resistance or voltage and with a dielectric layer in between as a function of its capacitance properties. Prior force (or pressure or weight) sensitive resistors have been developed which employ patterned surfaces having compressible conductive protrusions, peaks, fingers and the like or rigid conductive particles mounted on deformable bases. Such prior force sensors depend in their performance on force exerted on the tips or top ends of protrusions. When contact under force is made between the force sensor and the circuit or other conductive surface by which a circuit is to be closed, the tips or top ends of the protrusions can bend or buckle. Another disadvantage in using such systems is that the tips or top ends of protrusions provide a limited surface area for enabling electrical conductivity contact even if the peaks or protrusions are compressible. Prior force sensors also typically provide a relatively limited performance range over which conductivity may increase with pressure and vice versa.